Drawing upon research into a case study of teacher inquiry in one school in Queensland, Australia, recent theorising into professional practice, and relevant literature on teachers' learning, this article reveals the complexity and particularity of teacher inquiry processes in support of teachers' learning. Specifically, the research reveals how particular actions, dialogue, and relationships collectively constitute a practice of teacher inquiry which seeks to promote substantive teacher-led learning. The research draws upon a group of Year 5 teachers engaged in collective inquiry into their work in what was described as an "Inquiry Cycle" approach in a school in northern Queensland, during a period of support for substantial curriculum reform. The research reveals the Inquiry Cycle approach as characterised by specific actions, dialogue, and relationships--"doings," "sayings," and "relatings"--productive of the development of a learning culture focused on significant curriculum reform; overt support for whole-school "explicit" approaches to teachers' pedagogies; and active/robust critique of data-focused assessment processes. The research reveals necessary texture and detail in support of teachers' learning, and the specific circumstances and contextual "arrangements" that help constitute this learning.